46 FACTS ABOUT ROOTS 



offered them, the root hairs soon perish and with them the plant. 

 Continued absorption is only possible so long as the root continues 

 to grow. For this reason a plant showing signs of starvation is 

 removed from the jar, the tangled mass of roots next to the jar 

 is cut off together with a portion of the earth and then repotted 

 with fresh earth. In this way room is given for the rootlets to 

 grow out into the earth and develop a new absorbing surface and 

 additional materials are placed at the disposal of the root. We 

 see now that transplanting of the plant should be done in Sep- 

 tember or October or in the early spring in order to permit the 

 rootlets with their absorbing surfaces to become established in 

 the soil before the leaves develop and bring about an excessive 

 loss of water through transpiration. Why are plants often primed 

 or cut back in transplanting? 



You have often noticed that fields of grain and other crops turn 

 yellow and die during a long rainy season. This is due to the 

 fact that the air spaces between the earth particles become filled 

 with water and there is no longer possible an interchange of gases. 

 At least two-fifths of the space in these capillary pores should 

 be filled with air to ensure healthy plants. This is particularly 

 noticeable in clay soils which are referred to as cold, wet, and 

 sour soils. The reason of this is that the earth particles of such 

 soils are very fine and consequently compact and the small capil- 

 lary spaces between the mineral particles pull up and hold the 

 water with great tenactity. Consequently acids from decaying 

 vegetation and CO 2 from the roots as well as water accumulate 

 in excess and render the soil unwholesome. Clay soils, while 

 richer in plant foods than other soils require an admixture of 

 sand and an adequate drainage to render them sufficiently porous 

 for a proper circulation of air. Sandy soils are made of coarser 

 particles and therefore looser. For this reason the capillary 

 water is not retained for any considerable time and the soil is 

 properly aerated. Injudicious sprinkling of lawns, gardens, or 

 potted plants will result in the formation of a compact surface 

 crust. This acts exactly like a clay soil and draws the water 

 away from the region of the roots to the surface of the soil where 

 it is lost by evaporation. Potted plants are best watered by stand- 



